SBC 383 500ft/lb torque build

[Carnut1]

Gvx had a similar name but I am writing about Vincent.

[Scotthatch]

I have a novel idea ... use your real name a be a real person

[cjperformance]

I have a novel idea ... use your real name a be a real person

Most would not be so confident were the "cloak of mystery" removed from thier keyboard,, or is that "security blanket"!?

[groberts101]

I have a novel idea ... use your real name a be a real person

Most would not be so confident were the "cloak of mystery" removed from thier keyboard,, or is that "security blanket"!?

That's exactly why I only use my last name for my signin. Not comfortable telling people my name is Greg. Then I can talk all the crap I want and.. errr.. shit.. jiggs up now I guess.

[groberts101]

PS. 4.166 bore was mentioned above.. unless I missed something.. that must be a typo?

The head gasket itself bore I.D. size lol most gaskets for a SBC are from 4.060-4.200 it means a variation of a couple 1/10 in compression ratio no biggie in most cases. 4.166 and 4.146 are common sizes I end up with.

Ha.. I see that on the reread. That's what happens when you hit the keyboard and run. Lol

Btw.. i use the smallest damn gasket bore that fits the hole, highest top ring height, and usually dip well below .040 squish heights. Part of the reason I'm able to push the boundaries on pump gas.

[Carnut1]

Funny! Seems when a member is banned the old posts just have a member number.

[B Original]

Ha.. I see that on the reread. That's what happens when you hit the keyboard and run. Lol

Btw.. i use the smallest damn gasket bore that fits the hole, highest top ring height, and usually dip well below .040 squish heights. Part of the reason I'm able to push the boundaries on pump gas.

Actually I miss printed after looking at it again it's a couple .01's not .1's difference in compression.

My name is Marvin and my shop is B-Original no cloaks lol. After reading this forum for quite a while I've learned that there are a few on here that you just don't respond too unless it's a relevant response to the thread this way you don't contribute to the drama. I am sorry to say but I know several really good Minds and some of them personal friends that don't post or read on this forum anymore because of the un-nessasary sometimes salacious discord

[randy331]

B Original thank you very much for your help. The old time engine designer gave me information and I sourced parts accordingly:

350 30 over

3.75 stroke

5.7 rod

12cc 1.425 compression height pistons

0 deck true parallel to crank axis

.039 to .041 gasket

EQ CC167ES2 heads 76cc 2.02 1.60

CompCams X4258HR 1.5 rockers

Edel RPM performer Air Gap

650 - 750 cfm carb

Pump 87 octane

600 - 800 idle

I have sourced a roller block. Calculations come to approximately 9 to 1 static? Maximum torque in 2500 to 3500. I don't know if you can use the 5252 rule for horsepower? Cam timing may need to be retarded 4 degrees. Not sure need to play with that. Again thanks for your help.

Here is what I came up with It appears that you have 9.07-1 compression with a 4.166 hole X .041 head gasket. I found that the best balance and bang for the buck was to shave the head about .020 and raise your compression to 9.3-1 to make this recipe.
Attached below the TorqueMaster spec sheet is a comp cams grind with Terry Walters part#. You can order it through him for the same price as a Jegs or Summit shelf grind. I looked at comp, erson, and and Comp lobe profile was the closest and least aggressive for longer spring life.

This grind is a 264 duration cam although the program specs a 263. The 263 is not a common lobe master profile so I think it is the better alternative. the compromise is 15.8" idle vacuum instead of 16.1" vacuum
This will have a small but noticeable idle rumbly quality but you will have a huge flat torque curve above 2000 and wont fall off much below that.

Now for heads will be fine although your's have a 167cc intake port volume. The alternative the program specs is a 150cc version. The trade off will be a modestly shorter torque curve at lower end of the RPM's and a few more horsepower at the peak and maybe a 100 rpm or so increase in the predicted peak. If your heads flow more CFM at lift, along with the higher lift of this lobe profile will make the Horsepower#'s modestly higher at peak.


383 torque motor speedtalk mtmvette.jpg

383 torque motor speedtalk mtmvett comp 1.jpg

383 torque motor speedtalk mtmvett comp 2.jpg

No way to know any of this will turn out to be accurate on an actual engine until you try it, Then there is no way to know it couldn't be better until you try it a different way.

Those kinda sims are just for making you think you know it will be the best it can be without testing it.
Real world results will be different.

Randy

[groberts101]

B Original thank you very much for your help. The old time engine designer gave me information and I sourced parts accordingly:

350 30 over

3.75 stroke

5.7 rod

12cc 1.425 compression height pistons

0 deck true parallel to crank axis

.039 to .041 gasket

EQ CC167ES2 heads 76cc 2.02 1.60

CompCams X4258HR 1.5 rockers

Edel RPM performer Air Gap

650 - 750 cfm carb

Pump 87 octane

600 - 800 idle

I have sourced a roller block. Calculations come to approximately 9 to 1 static? Maximum torque in 2500 to 3500. I don't know if you can use the 5252 rule for horsepower? Cam timing may need to be retarded 4 degrees. Not sure need to play with that. Again thanks for your help.

Here is what I came up with It appears that you have 9.07-1 compression with a 4.166 hole X .041 head gasket. I found that the best balance and bang for the buck was to shave the head about .020 and raise your compression to 9.3-1 to make this recipe.
Attached below the TorqueMaster spec sheet is a comp cams grind with Terry Walters part#. You can order it through him for the same price as a Jegs or Summit shelf grind. I looked at comp, erson, and and Comp lobe profile was the closest and least aggressive for longer spring life.

This grind is a 264 duration cam although the program specs a 263. The 263 is not a common lobe master profile so I think it is the better alternative. the compromise is 15.8" idle vacuum instead of 16.1" vacuum
This will have a small but noticeable idle rumbly quality but you will have a huge flat torque curve above 2000 and wont fall off much below that.

Now for heads will be fine although your's have a 167cc intake port volume. The alternative the program specs is a 150cc version. The trade off will be a modestly shorter torque curve at lower end of the RPM's and a few more horsepower at the peak and maybe a 100 rpm or so increase in the predicted peak. If your heads flow more CFM at lift, along with the higher lift of this lobe profile will make the Horsepower#'s modestly higher at peak.


383 torque motor speedtalk mtmvette.jpg

383 torque motor speedtalk mtmvett comp 1.jpg

383 torque motor speedtalk mtmvett comp 2.jpg

No way to know any of this will turn out to be accurate on an actual engine until you try it, Then there is no way to know it couldn't be better until you try it a different way.

Those kinda sims are just for making you think you know it will be the best it can be without testing it.
Real world results will be different.

Randy

Right but nothing here is really new in the least. Sure each combo can vary slightly but this has all been done and repeated thousands of times over. So collectively, we have been sneaking up on more idealized combinations of parts until today. I wouldn't call this anything close to an idealized combo of parts, but hey to each their own. I see it as smacking yourself in the kneecap and then saying you're ready to run a marathon.

I still have a bit of bile coming up into my throat when I see that 4.166 gasket. .041 thick is really old school too, especially for such a lower rpm deal. Crevice volume makes a difference and you'll see it in the tune. As for the projected manifold vac readings listed there?.. I'd completely quit tuning ignitions and carb's if that motor didn't make it near 20" at idle.

[B Original]

I like that camshaft in a lot of ways ... about the same port efficiency of 85% but with better valve exposure at peak piston velocity... the overlap point looks great to ... but it takes out 5 degrees at ex opening point ...I was not sure opening at 40 on the last cam was early enough

Not sure if I understand what you are saying but wouldn't this reduce the scavenging potential by delaying the evacuation, and move the torque curve up the rpm range reducing the lower RPM torque?

[Scotthatch]

I like that camshaft in a lot of ways ... about the same port efficiency of 85% but with better valve exposure at peak piston velocity... the overlap point looks great to ... but it takes out 5 degrees at ex opening point ...I was not sure opening at 40 on the last cam was early enough

Not sure if I understand what you are saying but wouldn't this reduce the scavenging potential by delaying the evacuation, and move the torque curve up the rpm range reducing the lower RPM torque?

Your basic thinking is right my feeling is that it is delayed to far .... I have not found a good formula to calculate the opening point of the ex but my experience has been that a opening about 50 would make it run better .... with higher rpm motor 60 to 70 ... I'm sure some of it depends on the ex system and my general view on why is that you need to get the pressure low enough with the blowdown to not have the engine use energy on the upward stroke to push the gas past the valve ...

[B Original]

I like that camshaft in a lot of ways ... about the same port efficiency of 85% but with better valve exposure at peak piston velocity... the overlap point looks great to ... but it takes out 5 degrees at ex opening point ...I was not sure opening at 40 on the last cam was early enough

Not sure if I understand what you are saying but wouldn't this reduce the scavenging potential by delaying the evacuation, and move the torque curve up the rpm range reducing the lower RPM torque?

Your basic thinking is right my feeling is that it is delayed to far .... I have not found a good formula to calculate the opening point of the ex but my experience has been that a opening about 50 would make it run better .... with higher rpm motor 60 to 70 ... I'm sure some of it depends on the ex system and my general view on why is that you need to get the pressure low enough with the blowdown to not have the engine use energy on the upward stroke to push the gas past the valve ...

Purpose for the delay is a torque curve peak close to 3000 and more torque below 1500 and a flatter curve all over and lower rpm peak power 4500 specd in the program. This not a conventional motor its to make power below 5000 I have built 2 similar but they peaked in the mid 5000s with what you suggested a shorter exhaust opening.All three examples I referenced depend on sufficient exhaust scavenging. 29-31"+- primary's with a 2.25 pipe and free flowing mufflers

[B Original]

An afterthought considering what you are alluding to there probably is a point of diminishing returns and the longer exhaust lobe you describe like I've used previously may very well be on the The Fringe Edge of Maximum efficiency. The math looks right but practical application sometimes don't always agree with a math.

[Scotthatch]

Like I said I have had trouble calculating the opening point of the ex valve .... to early and you loose cylinder pressure that could do work ... to late and you build to much cylinder pressure during the ex phase that hurts how the engine revs ... and I agree that this engine is different .... I am so used to just looking at math for peak HP that it takes work to think torque ...that is why this thread attracted my attention .... the thing is the cam specs with moving the ex opening only to earlier is a odd cam if you draw it out .... I have over advanced cams before in my life some as much as 10 degrees this has proven to flatten and lower the power curve rpm but when I do that I have moved every event on the cam ... so was it just exposing the intake valve better or was it from moving the whole exhaust cycle to earlier